Method for fabricating selectively plated electrical contacts

ABSTRACT

A method and apparatus for making electrical contact members from a continuous sheet or tape of electrically conductive material, the members being provided with precisely located plated wear areas adapted to establish electrical connection with a mating contact. Apparatus is provided for indexing the tape with longitudinally spaced apart locating pilots, and for coating the tape with a resist material in a manner to define precisely located non-coated areas thereon, the non-coated areas corresponding to the wear areas of the contacts. Thereafter, the tape is subject to a selective plating process which plates only the non-coated wear areas with a layer of noble metal. Cleaning apparatus is provided for removing the resist material from the tape, and apparatus is provided for punching and forming the contacts from the tape, the apparatus being operative to precisely fixed the plated wear areas of the contacts with respect to the indexing pilots. In this manner, each of the contacts formed is provided with a precisely located plated wear area.

United States Patent [191 Healy et a1.

[ METHOD FOR FABRICATING SELECTIVELY PLATED ELECTRICAL CONTACTS [75]Inventors: Robert M. Healy, Warrenville;

' Ralph J. Hovey, Glen Ellyn, both'of Ill.

[73] Assignee: The Bunker-Ramo Corporation,

' Oak Brook, 111.-

[22] Filed: Jan. 10, 1972 [21] Appl. No.: 216,854

Related US. Application Data [62] Division of Ser. No. 815,609, April14, 1969,

abandoned.

[52] US. Cl. 29/630 C, 29/630 R, 29/630 B [51] Int. Cl. H01r 9/00' [58]Field of Search 29/630 R, 630 C;

[56] References Cited UNITED STATES PATENTS 3,537,175 11/1970 Clair etal. ll3/ll9R 3.420.087 l/l969 Hatfield et a1. 29/630 R 3.229.357 l/1966Burstin 29/630 C 3.537.971 11/1970 Green 204/206 3.579.822 5/1971Dieterich 29/630 3.137645 6/1964 Vaughan et a1 204/206 2,897,584 8/1954Schumpelt 200/166 C 1 Mar. 19, 1974 2 ,673,273 3/1954 Vasold ZOO/166 C3,675,320 7/1972 Watanabe 29/630 R 4/1951 Kleis et a]. 200/166 C 5 7ABSTRACT A method and apparatus for making electrical contact membersfrom a continuous sheet or tape of electrically conductive material, themembers being provided with precisely located plated wear areas adaptedto establish electrical connection with a mating contact. Apparatus isprovided for indexing the tape with longitudinally spaced apart locatingpilots, and for coating the tape with a resist material in a manner todefine precisely located non-coated areas thereon, the non-coated areascorresponding to the wear areas of the contacts. Thereafter, the tape issubject to a selective plating process which plates only the noncoatedwear areas with a layer of noble metal. Cleaning apparatus is providedfor removing the resist material from the tape, and apparatus isprovided for punching and forming the contacts from the tape, theapparatus being operative to precisely fixed the plated wear areas ofthe contacts with respect to the indexing pilots. In this manner, eachof the contacts formed is provided with a precisely located plated weararea.

1 Claim, 12 Drawing Figures METHOD FOR FABRICATING SELECTIVELY PLATEDELECTRICAL CONTACTS This is a division,'of application Ser; No. 815,609,filed Apr. 14, 1969 now abandoned.

BACKGROUND oF THE INVENTION The present invention relates generally tomanufacturing electrical contact members, and particularly to afabricating process and apparatus for rapidly and economically producinglarge quantities of selectively plated contact members in a continuousmanner.

An electrical contact member generally has a terminal portion to which aconductor or wire may be electrically connected and an engagementportion and surface adapted to mechanically engage and mate with asimilar portion and surface of another contact member. With use of thecontact members, the engagement surface becomes the active area of thecontact, subject to substantial ,wear. In the position in which twocontact members are fully mated or engaged, this engagement or wear areamust be substantially free of contamination or oxides which inhibit the'flow of electrical curcorrosive noble metals such as gold, usinggenerally conventional plating processes and apparatus.

l-Ieretofore the conventional method of plating large quantities ofcontact members has been the barrel type of process in which a largenumber of the contact members are placed in a perforated vessel which isrotated in an electrolytic plating solution of noble metal. A negativepotential is applied to the contacts by a conductoror electrode whichhangs loosely in the vessel. As the vessel rotates, the contact, memberstumble therein and intermittantly come into contact with the electrode.Plating current thereby passes to those members which directly contactthe electrode as well as those which in turn physically touch suchmembers. The members, however, that are not in physical contact with theelectrode or with other members that are in contact therewith, receiveno plating current. Thus,

plating current tends to benon-randomly applied to the contact membersduring a barrel type plating process. For this reason, the thickness ofthe deposited metal is not uniform from member to member.

Moreover, contact members are preferably made from spring metals such ascadmium bronze. When cadmium bronze is placed in a gold plating solutionand no electrical potentialis applied to the bronze the cad-J mium tendsto enter and contaminate the plating solution. To avoid suchcontamination, the sheet metal from which the contact members are madehas heretofore been first plated with a layer of copper to prevent thecadmium of the cadmium bronze metal from'coming directly into contactwith the gold plating solution.

When plating contact members of the type described the barrel type ofplating process is not economical of the plating metal in that theentire surface of each contact member is plated rather than just thewear area. If the plating metal is a precious metal such as gold, thecost and waste of such a plating process can be quite substantial.

A more recent approach to the problem of selectively coating largenumbers of electrical contacts is disclosed in US. Pat. No. 3,137,645,issued to R. T. Vaughan et al. on June 16, I964. The Vaughan et al.patent discloses apparatus wherein a limited area of a contact member isplated, the plating being accomplished by action of jet streams ofelectrolyte plating solution directed thereagainst. The jet streams areprovided ,by a

plurality of nozzles, and a chain of the contact members is-conductedpast the nozzles for the plating operation. While the Vaughan et al.apparatus does not plate the entire contact member the spraying actionprevents sharply defined plated areas from being formed.Consequently,'to ensure that a given thickness of metal will bedeposited on a given wear area of a contact member it is necessary toemploy a nozzle which produces a jet stream having an effective areasubstantially larger than the wear area. This is, of course, wasteful ofthe metal in the plating solution.

A further problem with the Vaughan et al process is that of cadmiumcontamination of the gold plating solution as explained above withrespect to the barrel type of plating process. Vaughan et al gravityfeed their plating nozzles from a reservoir of the plating solutionlocated above the nozzles. In the event of the loss of platingpotentials, the plating solution would continue to be directed againstthe contact members, with the possibility of the cadmium in the contactmembers entering into the solution of the plating metal.

BRIEF SUMMARY OF THE INVENTION Broadly, the present invention comprisesa method an apparatus capable of rapidly and economically mass producinglarge quantities of electrical contact members having plated portionsprecisely located on the active wear area and surface of each member.This is accomplished by first providing a sheetor tape of electricallyconductive material, the sheet or tape being of such a dimension thatsuccessive incremental lengths thereof serve as a plurality ofinterconnected blanks from which the contact members are formed. Thetape is next continuously provided with longitudinally spaced locatingindices or pilots, and then continuously, selectively coated with aresist material in a manner to define non-coated or bare areas thereoncorresponding to the wear areas, the non-coated areas being preciselylocated with respect to said locating pilots. The tape is nextcontinuously subjected to a plating solution of noble metal, said metaladhering only to the non-coated areas of the tape to form plated wearareas thereon. The resist material is then removed from the tape and theincremental lengths of the tape are subjected to a forming and punchingoperation. The apparatus for performing this operation engages thelocating pilots in a manner to accurately locate the plated wear areaswith respect to the pilots so that as each contact member is formed itis provided with a precisely located plate wear area with respect to theremaining portions of the contact member. Preferably, after the contactsare formed and separated from the tape, they are plated with anextremely thin layer of noble metal by an electroless plating operationto prevent the member from future tarnishing and oxidation.

The invention, as only briefly described thus far, provides a highlyeconomical method of plating electrical contacts that is particularlyuseful when the plating metal is a precious metal such as gold.

THE DRAWINGS The invention, with its objectives and advantages, will bebest understood from consideration of the following detailed descriptiontaken in connection with the accompanying drawings in which:

FIG. 1 is an enlarged side elevation view of a contact member fabricatedin accordance with the principles of the invention;

FIG. 2 shows apparatus for performing at least the initial step of theinvention through which an electrically conductive tape is provided withlocating indices or pilots;

FIG. 3 is a plan view of the tape produced by the apparatus of FIG. 2;

FIG. 4 is diagrammatic representation of a punching die embodied in theapparatus shown in FIG. 2;

FIG. 5 diagrammatically illustrates apparatus for performing a followingstep of the invention in which the tape is selectively coated with aresist material;

FIG. 6 shows the tape coated with the resist material;

FIG. 7 diagrammatically illustrates apparatus for performing furthersteps of the inventive process in which the tape is continuously,selectively plated and the resist material is thereafter continuouslyremoved from the tape;

FIGS. 8 through 88 represent various forms which the tape successivelytakes during yet another step of the invention in which electricalcontact members are formed from the tape;

FIG. 9 shows apparatus for forming the contacts of FIG. 8;

FIG. 10 shows means for performing a final plating step.

PREFERRED EMBODIMENT Specifically, FIG. 1 is an enlarged side view of aplated metallic contact member 10 made in accordance with the principlesof the invention. The contact 10 is of the type and configuration shownand described in U. S. Pat. No. 3,002,176, issued Sept. 26, I961, to R.S. Yopp and assigned to the present assignee. Such contact members aremade from a spring metal, such as cadmium bronze, and have mountingshank and terminal portions 12 and 14 respectively, and a contactengaging blade portion 16. The mounting and terminal portions are formedto have a three-sided channel shape adapted to seat in a cavity formedin a molded insulating connector, for example, as shown in theabove-mentioned Yopp patent. The terminal portion 12 is adapted to bejoined with an electrical conductor or wire (not shown). The bladeportion 16 is formed to engage and mate with a similar blade portion ofan opposite contact member in an active wear area defined by a layer ofnoble metal 17 deposited on a convex surface 18 of the blade inaccordance with the principles of the invention as hereinafterexplained. The blade 16 is further provided with a smoothly roundedconvex bulge or protuberance 20 on the convex surface portion 18 thereofso that the wear area of the blade includes the protuberance 20.

The layer of noble metal 17 on the blade 16 must be of a thicknesssufficient to insure against the metal of the blade surface 18 frombecoming exposed to the atmosphere. When oxidation begins to form evenin an extremely small portion of the wear area, the samll portionbecomes a source of contamination from which oxidation substances arespread to the remaining portions of the wear area. The spread of thecontamination is brought about when the use of the contact member isplaced in or removed from mating engagement with an identical or anothercontact member.

FIG. 2 shows apparatus for beginning the process of the invention. Moreparticularly, FIG. 2 shows a punch press 22, a tape 24 of spring metalmaterial, such as cadmium bronze, being continuously directed throughthe press from a feed reel 28 to a take-up reel 29. Between the pressand the take-up reel is located a vessel 30 through which the tape isconducted, the vessel representing a means for cleaning the tape.

The punch press 22 provides the tape with indexing or locating pilotholes 25 as shown in F IG. 3. This is accomplished by a punching die 26separately depicted in FIG. 4, the die 26 being a part of the punchpress 22.

The punching die 26 comprises essentially a tapered locating pin 26a anda punching or perforating pin 26b, the locating pin being longer thanthe punching pin. The tape 24 is successively advanced through the dieto undergo the punching process, the locating pin 26a fixing theposition of the tape for the punching pin 26b. In this manner, the pilotholes are formed and located in exact spacial relationship to each otherin a longitudinal direction.

The tape 24 is further fed through the punch press 22 and through thedie 26 with one edge of tape in sliding engagement with an edge or guide260, the edge or guide being shown in elevation in FIG. 4. In thismanner, the engaged edge of the tape functions as a fixed reference forthe lateral displacement of each pilot hole 25.

The holes 25 provided in the tape 24 act as locating indices or pilotswhich function to precisely locate the tape in the various operations tobe performed thereon. Although preferably in the form of apertures orslots these indices may be simply printed or embossed areas which areelectrically, photometrically or mechanically sensed in effecting thedesired locating function.

Successive incremental lengths 24' (FIG. 8) of the tape 24 as thus fardescribed, serve as a plurality of interconnected blanks from whichpluralities of contact members 10 (FIG. 1) are formed and punched in amanner explained hereinafter.

FIG. 5 shows diagrammatically apparatus for performing the next step ofthe invention. Specifically, FIG. 5 shows a printing apparatus 32 havingprinting rollers 34, a drying means 36, and feed and take-up reels 37and 39 respectively. The tape 24, after being indexed and cleaned by theprocess and apparatus of FIG. 2, is conducted through the printingrollers 34 in a continuous manner by drive means (not shown) driving thetake-up reel 39. The rollers 34 are adapted to coat the tape with aresist material on all areas thereof where a layer of a noble platingmetal is not desired. More particularly, at least one of the rollers isprovided with a pattern having a dimension corresponding to the platedwear area 17 of the contact member 10, the roller applying the resistmaterial in a manner to define the wear areas in discrete, non-coated orbare areas 40 as shown in FIG. 6. The non-coated areas 40 are preciselylocated with respect to the indexing holes 25 by virtue of indexingprojections 38 (only representively shown and provided on the upperroller in FIG. 5), the projections engaging the holes 25 as the tapepasses through the rollers. The projections are precisely lo- In apreferred embodiment of the invention the rollers 34 coat one side ofthe tape and both edges thereof 5 completely with the resist material,whereas the other side of the tape is provided with two rows of thenoncoated areas 40 as shown in FIG. 6. In this manner, the blank fromwhich the contact members will be formed, includes the area of the tapeencompassing two side-byside non-coated or bare areas 40 and anassociated pilot hole-25. From each blank, .two contact members will beformed and separated from the tape in a manner explained hereinafter.The number of contact members formed, however, from each blank may beone or more than two depending upon the dimensions of the tape and thecontact members to be formed therefrom. 1 1

After the resist material is applied to the tape 24, the material isdried and hardened thereon by the-drying means 36, only representivelyshown in FIG. 5, the tape being collected on the reel 39. I

The resist material employed in the coating process may be any materialcapable of being continuously applied and will adhere to the tape duringthe future selective plating process, yet can be removed from the tapeafter the'plating process. An example of such a material would beremovable ink such as flexog'raphic printing inks which are well knownin the printing art, though the invention is not limited thereto.

In a similar manner, the apparatus 32 may be any device capable ofapplying the resist material in'a controlled, continuous manner, forexample, a fiexographic printing press such as model 416 Webronlabelling machine, though other devices may be used.

F IG. 7 shows, schematically, apparatus for performing the nextsuccessive steps in the inventive process as thus far described. Moreparticularly, FIG. 7 shows enclosures or containers 41 for. performingcontinuously an additional cleaning operation upon the tape as it isremoved from a feed reel 41a and before it is conducted to anelectrolytic plating apparatus 42. Thereafpotential applied to the tapevia the brush 50, plating current is conducted through the solution tothe bare,

non-coated areas 40 of the tape to deposit the noble metal only onsaid'areas, the coating of resist material functioning as anelectrically resistive and substantially non-conductive material whichprevents plating on those surfaces of the tape covered by the resistmaterial. The plating metal deposits in a substantially uniform manneron the non-coated areas 40 to form the layer 17 (FIG. 1) having adesired thickness dimension, a desired thickness dimension beingpreferably in the order micro inches.

As can readily be appreciated, the only plating metal used in thepresent selective plating process is the metal applied to the wear areasof the contact. Substantially no metal is wasted, the plated metal beingconfined to the area of the contact where it is needed, namely, the

wear area.

Thus, when plating precious metals such as gold, substantial savings maybe-realized through the use of the present invention in contrast toprior art methods.

The solution of noble metal employed in the plating process of thepresent invention is preferably a hard,

- cobalt gold solution made from potassium gold cyater, the resistmaterial is continuously removed from the tape in enclosures orcontainers 44 located downstream from the plating apparatus 42, beforebeing collected on a take-up reel 45;

The plating apparatus 42 is schematically represented by an enclosure ortank 47 containing an anode plate or grid 48 electrically connected tothe positive side of a direct current power supply 49. The negative sideof the power supply is electrically connected to the tape 24 by a tapecontacting brush (only representatively shown by a circle 50 in FIG. 7)located downstream of the containers 44 employed for removing the resistmaterial. In this manner, a bare tape is available for making goodelectrical contact with the brush thereby making the tape a cathode forthe plating process. Beneath the tank 47 is located a container 52containing an electrolytic solution of noble plating metal. The solutionis directed to the enclosure 47 from the container 52, and returnedthereto after the plating process for subsequent plating use, thecontainer serving as a reservoir of the plating metal and solution.

In the plating process, the tape 24 is continuously conducted throughthe plating tank 47 and through the solution of noble metal containedtherein. With a positive potential applied to the anode 48, and anegative 'nide. An example of such a solution is the Autronex C IProcess Solution manufactured by the Sel Rex Corporation of Nulley, NewJersey, though other hard gold solutions are available and can be used.A hard gold is preferable for the active, wear area of each completedcontact. 10 to insure that the wear area remains completely providedwith a non-corrosive, non-oxidizing metal during the life of the contactmember or connector in which the member. is employed.

During the plating process, as long as the potentials are properlyapplied to the anode 48 and the tape 24, and current flow is in thedirection of the tape, the cadmium in the metal of the tape will notdissolve to any meaningful extent in the gold solution to contaminatethe solution, the direction of plating current tending to maintain thecadmium in combination with the copper of the tape as explained earlier.If, however, the application of the potentials is interrupted during theplating process, a means is provided for automatically draining thesolution of gold from the plating tank 47 before the cadmium hasopportunity to dissolve in and contaminate the gold solution. Such anautomatic draining means may include a sensing relay 53 (onlyrepresentatively shown in FIG. 7) electrically connected in the circuitof the power supply 49, and operative to effect the release of theplating solution to a container 53A when the relay senses the absence ofplating current. From the container 53A the solution may be returned tothe reservoir container 52 in a suitable manner. For this reason, in thepresent invention, it is not necessary to plate a cadmium bronze tapewith copper in order to prevent cadmium contamination of the goldsolution.

In FIG. 7, the apparatus for cleaning the blanks and for removing theresist material employs liquid spray nozzles located within thecontainers 4.1 and 44 for directing suitable cleaning liquids againstthe blanks though other means be employed in place thereof or inconjunction therewith. A suitable cleaning fluid would be normal alcoholwhich is a common, wellknown solvent for ink in the printing industry.

The tape may be drawn through the containers 41, 44 and the plating tank47 by a suitable drive means, for

example, by positive friction drive rollers 54 only diagrammaticallyindicated in FIG. 3. The rollers may be driven by a variable speed motor(not shown) connected to further drive the take-up reel 45 in a mannerwhich maintains suitable tension on the tape.

By controlling the speed at which the tape 24 is pulled through theplating tank 47 and/or by controlling the potential difference betweenthe tape and the anode plate 47, the desired thickness of the metalplate can be precisely controlled.

After the non-coated or bare areas 40 are plated and the tape iscollected on the take-up reel 45, the tape is ready for the process ofpunching and forming the completed, individual contact members 10.

In FIG. 9, a device 56 for performing this process is diagrammaticallydepicted, the device being a punch press 56 having contact forming andpunching dies 57. The press and dies operate in a manner to precieselylocate the area of each contact member on the tape before the contact isformed and separated from the tape. The dies 57 form and punch thecontact members in successive pairs from the tape, and the process bywhich the dies accomplish this is indicated in FIGS. 8 to 8B. The punchpress moves successive incremental portions 24 of the tape 24 from afeed reel 55 through its punching dies 57 in successive steps duringwhich portions of the metal encompassing the contact area aresuccessively punched away. The tape is precisely located in the dies bythe successive engagement of two pins of a pilot punch cooperating withan edge guide (not shown). The spacing of the pins relative to eachother and to the edge guide are the same as those of the punching die 26shown in FIG. 4. In this manner, the contacts are precisely located withrespect to the indexing pilots so that when the contacts 10 are finallyformed and severed from the tape, the plated wear area 17 of eachcontact member 10 is precisely located with respect to the remainingportions ofthe contact memher.

As the contact members 10 are formed in pairs, as shown in FIGS. 8A andB, and the metal is cut away by the dies 57, a portion 58 of each blankassociated with a pilot hole 25 serves essentially as a carrier portionwhich carries each pair of contacts until the contacts are finallysevered therefrom. The severed, completed contacts are collected in acontainer 59 as shown in FIG. 9.

The punch press 56, and the operation thereof, as described above, isbasically that of a multi-slide machine manufactured by the UnitedStates Tool Company. In the present invention, however, other types ofcontact member forming machines and devices may be used withoutdeparting from the spirit and scope thereof.

After the contact members 10 are formed and separated from the tape 24,the unplated portions of the contact members are plated with anextremely thin layer of a noble metal in order to prevent the membersfrom future tarnishing. A suitable thickness for the thin layer would beon the order of two to five micro inches. This is accomplished by anelectroless, immersion type of plating process as diagrammaticallyindicated in FIG. 10, the contact members being placed in a basket 60 orother suitable container and lowered into a solution 62 of the platingmetal.

An electroless plating process is a preferential plating process inwhich the noble metal, (for example, a substantially pure, soft gold)exchanges places with the metal of the part to be plated on an ionexchange basis. The thickness of the plating produceable by this type ofprocess is limited as in the case of gold to a few micro inches sincethe heavier the deposition of the gold on the part the more theelectroless plating process is inhibited. The electroless process isparticularly suitable for purposes of the present invention since thethickness of the plating is substantially that required to provide thenon-tarnishing, thin layer of soft gold over the portions of eachcontact members not covered by the heavier layer of noble metal 17. Theelectroless type of plating operation is a well-known process, and thereare a variety of gold solutions available for this type of platingprocess.

In the description of the present invention, the term noble metal isrepresentative of any substantially inert, non-corrosive ornon-oxidizing metal suitable to maintain the surfaces of the contactmembers 10 free from contaminating substances which would adverselyaffect their ability to conduct electrical current when disposed inmating engagement with other contact members.

From the foregoing description it should now be ap parent that thepresent invention provides a new and useful process and apparatus forrapidly and continuously fabricating plated electrical contact membersin an economical manner. This is accomplished by first providing acontinuous tape of spring metal material with locating pilots. The tapeis next continuously directed through a coating device, the coatingdevice applying a resist material to the tape in a manner to preciselydefine bare areas thereon corresponding to wear areas of the contactmembers. Thereafter the tape is continuously subject to a platingprocess in which a layer of noble or other non-corrosive metal isapplied to the bare areas only. The resist material is continuouslyremoved from the tape and the tape is next subjected to a contactforming operation in which the plated wear areas are successively andprecisely fixed with respect to the locating pilots before the contactmembers are formed and punched from the tape. In this manner, eachcompleted contact member is provided with a plated wear area that isprecisely located with respect to the remaining portions of the contactmember.

Though the invention has been described with a certain degree ofparticularity, changes may be made therein without departing from thespirit and scope thereof.

What is claimed is:

l. A continuous method of fabricating electrical contact members of thetype wherein each member has a wear area adapted for mating engagementwith another contact member to establish electrical connectiontherewith, and a terminal portion adapted to be joined to an electricalconductor, the method comprising the steps of:

providing a long, thin, narrow, flexible spring metal tape of suchdimensions that successive incremental lengths of the tape are adaptedto act as plurality of interconnected contact blanks from which saidcontacts are punched,

advancing said tape longitudinally in successive steps through the diesof a punch-press and punching at least one series of regularly spacedpilot holes therein,

thereafter feeding said tape through a printing means by successiveengagement of indexing means of the printing means with the pilot holesin the tape, and printing on resist material on both edges and bothsides of said tape, with the printing on at least one side of said tapecomprising a regularly recurring pattern of resist materialcharacterized by at least one bare area surrounded by said resistmaterial for each contact member to be produced corresponding to thewear area of each completed contact and located in precise spacialrelationship to the aforesaid pilot holes in said tape,

thereafter subjecting said tape to a selective plating process whereby alayer of a substantially inert, non-corrosive metal of a desiredthickness is apeach contact member formed.

1. A continuous method of fabricating electrical contact members of thetype wherein each member has a wear area adapted for mating engagementwith another contact member to establish electrical connectiontherewith, and a terminal portion adapted to be joined to an electricalconductor, the method comprising the steps of: providing a long, thin,narrow, flexible spring metal tape of such dimensions that successiveincremental lengths of the tape are adapted to act as plurality ofinterconnected contact blanks from which said contacts are punched,advancing said tape longitudinally in successive steps through the diesof a punch-press and punching at least one series of regularly spacedpilot holes therein, thereafter feeding said tape through a printingmeans by successive engagement of indexing means of the printing meanswith the pilot holes in the tape, and printing on resist material onboth edges and both sides of said tape, with the printing on at leastone side of said tape comprising a regularly recurring pattern of resistmaterial characterized by at least one bare area surrounded by saidresist material for each contact member to be produced corresponding tothe wear area of each completed contact and located in precise spacialrelationship to the aforesaid pilot holes in said tape, thereaftersubjecting said tape to a selective plating process whereby a layer of asubstantially inert, non-corrosive metal of a desired thickness isapplied only to the bare areas of said tape, thereafter removing theprinted resist material pattern from all areas on said tape, againadvancing said tape longitudinally in successive steps through the diesof a punch-press, and subjecting each incremental length of said tape toat least one punching operation followed by at least one formingoperation to form each contact member with a plated wear area inprecisely fixed spacial relationship with respect to the pilot holes ofsaid tape, whereby the plated wear area is precisely located withrespect to the remaining portion of each contact member formed.